In recent years the need to exploit oil resources at very considerable depths has been observed; this phenomenon has been the cause of multiple problems in the drilling and finishing techniques for oil wells, particularly in the application of slurry for cementing and recementing oil wells, since the internal temperature of the well becomes higher as its depth increases, which causes a faster setting of the slurry and makes its handling more difficult.
In the drilling, finishing and repair operations of oil wells cementing of the casings is employed; this technique is conducted by introducing a cement slurry to the bottom of the oil well through the cementing pipe; the slurry is placed in the annular space between the casing and the well walls, where it sets more or less rapidly, depending on the prevailing temperature.
In order to overcome the disadvantages of the immediate setting of the cement slurry, the applicant has carried out research activities.
In U.S. Pat. No. 3,905,826, having the same assignee as the instant invention, a setting retarding composition is described which has as basic ingredients carboxymethylcellulose, dextrine, borax, and optionally organic salts, and it presents as novel feature the fact that it can be applied with good results at depths of up to 13123.4 ft.